Now, this is just speculation. Based on nothing. But perhaps they cast Sherie because they knew how beloved Idina was. Kristen's Maureen is relatively similar to Idina's, right? So maybe they wanted something completely different so (they thought) the two couldn't be compared. Like when my highschool did Les Mis back in the day and followed it up with Anything Goes. The two are so drastically different, they can't reasonably be compared. Maybe their reasoning just backfired on them? Again, just speculation.
"`I grow old... I grow old... I shall wear the bottoms of my trousers rolled.` What does that mean, Mr. Marlowe?"
"Not a bloody thing. It just sounds good."
He smiled. "That is from the `Love Song of J. Alfred Prufrock.` Here's another one. `In the room women come and go/Talking of Michael Angelo.' Does that suggest anything to you, sir?"
"Yeah -- it suggests to me that the guy didn't know very much about women."
"My sentiments exactly, sir. Nonetheless I admire T. S. Eliot very much."
"Did you say, 'nonetheless'?"
- The Long Goodbye by Raymond Chandler